| Two-dimensional materials refer to materials with a thickness of only a few atomic layers.Compared with traditional three-dimensional materials,two-dimensional materials have a high chemical and physical surface area,and exhibit unique physical,electrical,and optical properties.Since the discovery of graphene,research on two-dimensional materials has received great attention.Studies have shown that many two-dimensional materials have excellent electrical properties,including high carrier mobility and conductivity,lower carrier concentration and noise levels,which make them promising for electronic devices.In addition,many two-dimensional materials also have excellent optical properties,such as high absorption coefficients,wide optical response range,and long lifetimes.These properties make two-dimensional materials exhibit great potential in optoelectronics,such as applications in solar cells,photodetectors,and optical sensors.In this article,several new two-dimensional semiconductor materials with narrow band gaps and excellent optoelectronic properties were predicted based on first-principles calculations,and their stability,electronic structure,and optical properties were studied using calculation software systems such as VASP.The main research contents are as follows:Two-dimensional AOBi X2（A=Sc,Y;X=S,Se）has good stability,and the band gap,effective mass,and optical absorption capacity were calculated.The research results show that the band gap of two-dimensional AOBi X2 is in the range of 0.66 e V～1.12 e V.Among them,two-dimensional YOBi S2 has a direct band gap with a value of 0.58 e V.The other three materials exhibit indirect band gaps.At room temperature,the carrier mobility of two-dimensional AOBi X2 ranges from 3.22 cm2·s-1·V-1to 870.93 cm2·s-1·V-1,and the two-dimensional YOBi S2 has the highest carrier mobility of 870.93 cm2·s-1·V-1.In the visible light range,the optical absorption coefficient of two-dimensional AOBi X2 is above 105 cm-1,and two-dimensional YOBi S2has an optical absorption coefficient as high as5.5×105 cm-1.These results indicate that the material has good stability and excellent optoelectronic properties,making it an ideal material for the preparation of infrared photodetectors and optoelectronic memories.Through calculations based on density functional theory and the VASP software package,a systematic study was conducted on the crystal structure,stability,exfoliation energy,electronic structure,and optical properties of 2D rare earth chalcogenide compounds AOBi X2（A=La,Pr,Nd;X=S,Se）.The results show that 2D AOBi X2 has good stability and can be prepared through mechanical exfoliation.The electronic structure calculation results indicate that 2D AOBi X2 has a direct bandgap ranging from 0.52 e V to 0.71 e V,with 2D Pr OBi S2 exhibiting the highest electron mobility(～2940.27 cm2·s-1·V-1).The calculated optical absorption coefficients of the six materials in the visible range are all above 105 cm-1,with the absorption edge positions distributed between 0.52 e V and 0.71e V.2D AOBi X2 has excellent stability and optoelectronic properties,making it an ideal material for the preparation of infrared photodetectors and optoelectronic memories.In addition,these materials can also be applied in other fields,such as solar cells,photocatalysis,and sensors.Finally,2D materials APO（A=Ti,Hf,Zr）with a monoclinic crystal system and space group P2/C were studied.The lattice parameters,atomic positions,and energy information were obtained through calculations,and the stability of the material was demonstrated.Electronic structure calculations and analysis revealed that 2D APO is a direct bandgap semiconductor material,with effective mass ranging from 0.25 m0 to 0.55m0,with 2D Ti PO exhibiting the highest carrier mobility for holes along the X→Γdirection(335.49 cm2·s-1·V-1).In the visible range,2D APO all have absorption coefficients above 105 cm-1.The materials studied in this paper have high application potential and can be used to prepare infrared photodetectors,optoelectronic memories,solar cells,photocatalysts,and sensors,among other applications.These materials have excellent optoelectronic properties,enabling high sensitivity,high response speed,and low noise,and have broad application prospects and important value in various fields. |
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